Frequently we look for a queen in a hive. And if we can't find the queen, we look to see if there are eggs. But in the absence of a queen and open worker brood, a worker may start laying. Usually eggs from laying workers may be up on the side of a cell since their abdomens are not long enough to get all the way down. Or there may be multiple eggs in a cell. And the capped brood will be drone brood. These are signs of a laying worker.
Workers will lay their eggs in any available cell. So you can not judge by the diameter of a cell like you can with drone brood from a queen. However, once capped the drone brood cell will stick up like normal drone brood.
When considering a split, it's important to have drones around to mate with the queen. But drones from laying workers don't count. They don't have what it takes to mate a queen.
Queen cells charged with an egg from a laying worker will not be a good queen.